Chapter 9 Moving verbs in agrammatic production

166 Grammatical disorders i n aphasia
10-14% of the sentences, and there is no reason to believe that agrammatics
would prefer to use auxiliary constructions in 53% of the sentences,
and then omit the auxiliary. True, agrammatics do use forms that usually
require an auxiliary verb, but only because the forms they use arc forms
that do not carry tense, and therefore in normal syntax require an; auxiliary
to carry the inflection.
Verb omission: averbia or inflectional deficit
Agrammatics frequently omit verbs in spontaneous speech and in picture
description. This led researchers to claim that agrammatics have an
additional problem: averbia (see for example Zingeser and Berndt, 1990).
That is - in addition to their other deficits, they also have a special
problem in the lexicon that prevents them from retrieving verbs.
In the Bastiaanse and Van Zonneveld (1998) study, Dutch-speaking
agrammatics had 'verb retrieval' deficits in second position only (where
the verb has to be inflected) but not in sentence final position (where it
appears in a low node). This finding cannot be explained by lexical
retrieval deficit. It indicates, rather, the strong relation between verb
production and its sentential position, and raises the possibility that
agrammatics omit verbs not due to a lexical retrieval deficit, but due to
their inability to move them to the relevant functional categories in the
syntactic tree and to inflect them correctly.
Another corroboration for this claim comes from a tense treatment study:
Weinrich, Shelton, Cox and McCall (1997) report that their patients had
severe tense-inflection deficit before treatment: they inflected only 5% and
17%, 22% of their verbs correctly for tense. At that stage, their patient also
had verb-retrieval deficit: they produced only 36%, 43% and 53% of the
required verbs. After treatment of tense production, when their tense inflection
has improved significantly (to 92, 64 and 73% correct), their verb
retrieval ability had strikingly doubled (to 89, 85 and 83%). This again
suggests the involvement of inflection in verb production.
This poses a new type of explanation for verb omission in terms of verb
movement. When agrammatics have to inflect a verb and move it to a
pruned position, they sometimes prefer not to produce the verb at all. The
deficit, then, is not a purely lexical deficit in the 'verb lexicon'. It is
modulated, rather, by syntactic structure, and can be explained within the
framework of pruned trees and the resulting verb movement deficit.
Thus, verb omissions may result from the same deficit that causes verb
inflection errors: a syntactic deficit.
Infinitives in Hebrew
One of the important properties of the infinitives that are used in agrammatic
production instead of inflected verbs is that they arc bare infini-
Moving verbs in agrammatic production 167
Lives: namely, they do not contain the 'to' morpheme. Agrammatics
produce sentences of the form, but do not produce sentences like (13).
12. Dori drive a Porsche
Dori to drive a Porsche
It is now clear why aphasics use verbs without the 'to' morpheme (see, for
example, 'to' omissions in English and Dutch in Menn and Obler, 1990):
'to' is a tense morpheme, and is located in Tense node which is located in
the pruned part of the tree. Whereas bare infinitives are licensed in low
nodes, their inflection 'to' is not.
Consider the implications this has for the choice of replacing forms in a
language that does not have a bare verb, and where its infinitive includes
the 'to' as a bound inflection. In such a language, the infinitive also has to
move up to tense node to collect (or check) its inflection. In this case,
infinitives are expected not to be produced instead of finite verbs.
Fortunately we can test this in Hebrew, seeing as Hebrew is a language
in which the infinitive is not bare. The Hebrew infinitive contains a
morpheme which is the analogue of 'to' (the prefix 'le-'), and it is therefore
parallel to the whole phrase 'to go' in English, and not only to the
bare verb 'go'. Therefore, the infinitive in Hebrew must raise high like an
inflected verb, to check its inflection. Another demonstration for the
difference between the Hebrew infinitive and the English infinitive is the
fact that the Hebrew infinitive does not appear as a complement of auxiliary
verbs. Because it is inflected and occupies the Tense node, there is no
place or need for an auxiliary. Furthermore, the movement pattern of the
infinitive in Hebrew is just the same as the movement of the finite verb:
arguments from word order of adverbs and infinitives show that they
raise to the same high node in the syntactic tree as finites (Shlonsky,
1997).
The prediction, then, is that in Hebrew, unlike in German and Dutch,
for example, infinitives will not be overused in agrammatic production.
This prediction was tested in 11 Hebrew-speaking agrammatic patients
(Friedmann, 1998).
Sentence repetition and verb completion in sentential context were
used to assess inflection abilities and to find out whether agrammatic
aphasics use infinitives instead of finite verbs in Hebrew. Errors were
analysed in order to determine whether agrammatics substituted the
infinitive for finite verbs, or kept all verb inflection errors within the finite
paradigm.
The results were clear-cut: substitution errors were almost always
within the finite paradigm (or possibly included substitution of the
participle which is identical to the present tense). Errors were substitution
of one tense for another, but almost never substitution of infinitival form
for the finite. 9 Again, each individual patient showed the same pattern of